1. Field of the Invention
The present invention relates to preparation of a highly pure copper oxide from waste etchant created when a printed circuit board (PCB) is fabricated, more particularly, to preparation of a highly pure copper oxide from waste etchant in which alkali aqueous solution (sodium hydroxide or potassium hydroxide) is added to a waste etchant to obtain copper hydroxide and then the copper hydroxide is dehydrated to form copper oxide which has a high purity (99.0 wt %) and an excellent filtration ability.
2. Description of the Background Art
Printed Circuit Boards are widely used in many electronic computer devices. A chemical milling process is commonly utilized in manufacturing printed circuit boards. In a typical chemical milling process, an etchant solution etches the copper plated printed circuit board. One of the most common etchants in the electronic and computer industries is acidic copper chloride etchant which consists of hydrochloric acid (HCl) and copper chloride (CuCl2). It has posed a substantial environment problem to dispose of spent etchant without proper treatment because the spent etchant contains a considerable amount of copper (10-15 w %). In addition, disposing of spent etchant without treatment results in great economic loss. Accordingly, recovery of the copper component from the waste etchant produced in the PCB industry is important in view of recycling a resource and reducing an environmental pollution.
Though the composition of acidic waste etchant may be different by PCB fabricating companies, it typically contains 19xcx9c25 wt % of CuCl2, 7xcx9c10 wt % of HCl, 64.5xcx9c74 wt % of H2O.
A conventional method for preparing copper oxide is disclosed in a literature (J. Korean Solid Waste Engineering Society, Vol. 14, No. 7, 667-672, 1997) in which basic waste etchant (composition: Cu(NH3)Cl, NH4NO3, (NH4)2CO3 and NH4OH) is added quantitatively to acidic waste to obtain precipitation, and then the precipitation is sintered to obtain copper oxide.
However, with this method, since the basic copper chloride waste etchant itself contains quite a few amount of heavy metals as impurities, the recovered copper oxide accordingly contains the heavy metals as impurities. Thus, the copper oxide prepared using this method is not suitable to use for a high purity reagent or for semiconductor device. Thus, this method indispensably needs a process to purify and remove the impurity.
The Korean Patent No. 96-775 discloses a method for preparing copper oxide from an acidic copper chloride waste etchant through which ammonia gas passes to thereby fabricate a copper-ammonia complex. An additional amount of sodium hydroxide is added to a copper-ammonia complex to produce copper oxide. This method, however, is disadvantageous in that since a large quantity of ammonium chloride by-product is created, an additional expense is incurred to process the by-product, accounting for a great percentage of its production cost.
Thus, the inventors of the present invention has developed an environmental-friendly and cost-effective process for preparing copper oxide of homogeneous particle size, and attained an improved method for synthesizing copper oxide.
In detail, according to the newly attained method by the inventors of the present invention from the research, when acidic copper chloride waste etchant was neutralized by controlling pH and temperature, blue copper hydroxide and sodium chloride as by-products were recovered. When this slurry was heated at a temperature of 50xcx9c100xc2x0 C., it was observed that the slurry was changed to copper oxide of a needle form with homogeneous particle size distribution.
Therefore, an object of the present invention is to provide a method for preparing copper oxide where alkali aqueous solution is added to an acidic copper chloride waste etchant (composition: 19xcx9c25.5 2t % of CuCl2, 7xcx9c10 wt % of HCl and 64.5xcx9c74 wt % of H2O) created in fabricating a PCB to produce copper hydroxide as an intermediate, and the copper hydroxide is heated to obtain copper oxide having a more than 99.0 wt % of purity and excellent filtration ability.
To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described herein, there is provided a method for preparing copper oxide, including: a first step in which a sodium hydroxide aqueous solution is added to an acidic copper chloride waste etchant produced in the PDB industry, to obtain copper hydroxide slurry; and a second step in which the slurry obtained in the first step is heated and sintered to thereby fabricate a needle-form copper oxide having a purity of more than 99.0 wt %.
The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention.